Currently, various types of wireless communication technologies, which are necessarily used in our daily lives, are in rapid development.
In particular, services using wireless communication such as radio frequency identification (RFID)/ubiquitous sensor network (USN), wireless broadband Internet (WiBro), and the like in addition to mobile communication, wireless local area network (WLAN), digital broadcasting, and satellite communication, are significantly increasing. Due to diversification of wireless communication service, which has had a sudden increase in development, and an increase in use thereof, a demand for limited frequency resources is increasing and a value thereof is also gradually increasing. To efficiently utilize such important electric wave resources, advanced countries are actively conducting an activity for developing a technology of efficiently utilizing the electric wave resources and establishing an electric wave policy based thereon.
In this regard, proposed is a cognitive radio (CR) capable of sensing an idle frequency, which is allocated but is not actually used, and efficiently sharing and thereby using the sensed idle frequency.
The cognitive radio indicates a technology that automatically finds an unused frequency based on a region and time, and enables targeted communication while protecting a permitted neighboring radio station. By finding an idle spectrum that is widely dispersed over various widths and of which occupancy time continuously varies, and by determining a frequency bandwidth, output, a modulation scheme, and the like suitable for an environment of the found idle spectrum, and thereby enabling the found idle spectrum to be reutilized, it is possible to increase efficiency of frequency that is a limited resource. The Institute of Electrical and Electronics Engineers (IEEE) has been implementing a technology standardization using a cognitive radio (CR) of television (TV) frequency band since 2004.